Controlling the localized flow rate of a deposition material in a deposition process (such as the ion flux in an electrolytic deposition process), to effect greater uniformity of coating on a planer substrate, is well known. See, for example, U.S. Pat. No. 4,304,641 issued to Grandia et al. and assigned to IBM; No. 5,391,285 issued to Lytle et al. and assigned to Motorola; and No. 5,435,885 issued to Jones et al. and assigned to IBM. The use of overlapping baffle plates with a series of openings to control total neutron flow rate in a nuclear reactor is seen in U.S. Pat. No. 5,023,044 issued to Negron and assigned to Babcock & Wilcox.
Notwithstanding these prior art teachings, there remains a need to improve the uniformity of a deposited coating irrespective of position on the deposition substrate. This need is particularly acute in the electrolytic plating of electronic components, wherein uniformity of thickness throughout the area of the coating is a significant factor in the performance of the component. A non-uniform coating may require excessive post-coating treatment (such as chemical mechanical polishing) to obtain the necessary thickness uniformity.